Final answer:
An anticoagulant is a substance that opposes coagulation, or the formation of blood clots. Inverting the tube helps prevent clot formation.
Step-by-step explanation:
An anticoagulant is a substance that opposes coagulation, or the formation of blood clots. In the context of the question, using an anticoagulant tube would help prevent clot formation. By inverting the tube, the anticoagulant mixes with the blood, preventing it from clotting.